1. Field of the Invention
The invention relates to a can and a lithium secondary battery using the same. More particularly, the invention relates to a can and a lithium secondary battery using the same wherein electrolyte can be easily introduced into the can even if a jellyroll-type electrode assembly has been accommodated in the can, and the amount of the electrolyte contained in the can may be increased.
2. Description of the Prior Art
Recently, light-weight portable wireless appliances, such as video cameras, portable phones and portable computers, have been fabricated and equipped with various functions, and studies have been actively performed in relation to secondary batteries used as power sources for the portable wireless appliances. For instance, the secondary batteries include Ni—Cd batteries, Ni-MH batteries, Ni—Zn batteries and lithium secondary batteries. Among other things, the lithium secondary batteries are rechargeable batteries, which can be compact in size with high capacity. The lithium secondary batteries can deliver high operational voltage and high energy density per unit weight, so the lithium secondary batteries are extensively used in the advanced electronic technology fields.
FIG. 1 is an exploded perspective view illustrating a conventional lithium secondary battery.
The conventional lithium secondary battery can be obtained by accommodating an electrode assembly 112 including a positive electrode plate 113, a negative electrode plate 115 and a separator 114 in a can 110 together with an electrolyte, and then sealing an upper opening 110a of the can 110 using a cap assembly 120.
In general, the can 110 is made from aluminum or an aluminum alloy through a deep drawing process. In addition, a lower surface 110b of the can 110 is substantially planar.
The electrode assembly 112 is formed by winding the positive electrode plate 113 together with the negative electrode plate 115 while interposing the separator 114 therebetween. A positive electrode tap 116 is coupled to the positive electrode plate 113 and an end portion of the positive electrode tap 116 protrudes upward from the electrode assembly 112. A negative electrode tap 117 is coupled to the negative electrode plate 115 and an end portion of the negative electrode tap 117 protrudes upward from the electrode assembly 112. The positive electrode tap 116 is spaced apart from the negative electrode tap 117 by a predetermined distance such that the positive electrode tap 116 can be electrically insulated from the negative electrode tap 117. In general, the positive and negative electrode taps 116 and 117 are made from nickel.
The cap assembly 120 includes a cap plate 140, an insulating plate 150, a terminal plate 160 and an electrode terminal 130. The cap assembly 120 is accommodated in an insulating case 170 and assembled to couple with the upper opening 110a of the can 110, thereby sealing the can 110.
The cap plate 140 is made from a metal plate having a size and a shape corresponding to those of the upper opening 110a of the can 110. The cap plate 140 is formed at the center thereof with a first terminal hole 141 having a predetermined size and the electrode terminal 130 is inserted into the first terminal hole 141. When the electrode terminal 130 is inserted into the first terminal hole 141, a gasket tube 146 is fitted around the electrode terminal 130 in order to insulate the electrode terminal 130 from the cap plate 140. An electrolyte injection hole 142 having a predetermined size is formed at one side of the cap plate 140. After the cap assembly 120 has been assembled with the upper opening 110a of the can 110, the electrolyte is injected into the can 110 through the electrolyte injection hole 142. Then, the electrolyte injection hole 142 is sealed by means of a plug (not shown).
The electrode terminal 130 is connected to the negative electrode tap 117 of the negative electrode plate 115 or the positive electrode tap 116 of the positive electrode plate 113 so that the electrode terminal 130 may serve as a negative electrode terminal or a positive electrode terminal.
The insulating plate 150 is made from an insulating material identical to the material for the gasket and is coupled with the lower surface of the cap plate 140. The insulating plate 150 is formed with a second terminal hole 151, which is aligned corresponding to the first terminal hole 141 of the cap plate 140 and into which the electrode terminal 130 is inserted. The insulating plate 150 is formed on the lower surface thereof with a resting recess 152 having a size and a shape corresponding to those of the terminal plate 160 such that the terminal plate 160 can be rested in the resting recess 152.
The terminal plate 160 is made from a Ni alloy and is coupled with the lower surface of the insulating plate 150. The terminal plate 160 is formed with a third terminal hole 161, which is aligned corresponding to the first terminal hole 141 of the cap plate 140 and into which the electrode terminal 130 is inserted. Since the electrode terminal 130 is inserted into the first terminal hole 141 of the cap plate 140 and is insulated from the terminal plate 140 by means of the gasket tube 146, the terminal plate 160 can be electrically connected to the electrode terminal 130 while being electrically insulated from the cap plate 140.
The negative electrode tap 117 coupled to the negative electrode plate 115 is welded to one side of the terminal plate 160, and the positive electrode tap 116 coupled to the positive electrode plate 113 is welded to other side of the cap plate 140. The negative and positive electrode taps 117, 116 are welded to the terminal plate 160 and the cap plate 140 through resistance welding or laser welding. In general, the resistance welding is employed.
Recently, in order to obtain a lithium secondary battery having high capacity, the area of the electrode plate of the electrode assembly was enlarged, the winding number for the electrode assembly was increased, and the thickness of the electrode assembly was enlarged. However, if the thickness of the electrode assembly is increased, it is difficult to ensure a sufficient gap between the electrode assembly and the can when the electrode assembly has been accommodated in the can. In this case, it is difficult to inject the electrolyte into the can after the cap assembly has been welded to the upper portion of the can having the electrode assembly because the electrolyte may not uniformly flow into the can. In addition, when the electrode assembly has been accommodated in the can, only a small empty space is formed in the can, so the amount of electrolyte contained in the can is reduced.